subroutine calcDoubleR2L2R_stochastic(ilut, csf_i, excitInfo, t, branch_pgen, &
posSwitches, negSwitches, opt_weight)
integer(n_int), intent(in) :: ilut(0:nifguga)
type(CSF_Info_t), intent(in) :: csf_i
type(ExcitationInformation_t), intent(in) :: excitInfo
integer(n_int), intent(out) :: t(0:nifguga)
real(dp), intent(out) :: branch_pgen
real(dp), intent(in) :: posSwitches(nSpatOrbs), negSwitches(nSpatOrbs)
type(WeightObj_t), intent(in), optional :: opt_weight
character(*), parameter :: this_routine = "calcDoubleR2L2R_stochastic"
integer :: iOrb, switch
type(WeightObj_t) :: weights
real(dp) :: temp_pgen
HElement_t(dp) :: integral
associate (i => excitInfo%i, j => excitInfo%j, k => excitInfo%k, &
l => excitInfo%l, start1 => excitInfo%fullstart, &
start2 => excitInfo%secondStart, ende1 => excitInfo%firstEnd, &
ende2 => excitInfo%fullEnd, typ => excitInfo%typ)
ASSERT(.not. isThree(ilut, start1))
ASSERT(.not. isZero(ilut, start2))
ASSERT(.not. isThree(ilut, ende1))
ASSERT(.not. isZero(ilut, ende2))
if (present(opt_weight)) then
weights = opt_weight
else
! : create correct weights:
weights = init_fullDoubleWeight(csf_i, start2, ende1, ende2, negSwitches(start2), &
negSwitches(ende1), posSwitches(start2), posSwitches(ende1), &
csf_i%B_real(start2), csf_i%B_real(ende1))
end if
call createStochasticStart_single(ilut, csf_i, excitInfo, weights, posSwitches, &
negSwitches, t, branch_pgen)
! check validity
check_abort_excit(branch_pgen, t)
do iOrb = start1 + 1, start2 - 1
call singleStochasticUpdate(ilut, csf_i, iOrb, excitInfo, weights, posSwitches, &
negSwitches, t, temp_pgen)
! check validity
branch_pgen = branch_pgen * temp_pgen
check_abort_excit(branch_pgen, t)
end do
! change weights... maybe need both single and double type weights
! then do lowering semi start
weights = weights%ptr
call calcLoweringSemiStartStochastic(ilut, csf_i, excitInfo, weights, negSwitches, &
posSwitches, t, branch_pgen)
! check validity
check_abort_excit(branch_pgen, t)
do iOrb = start2 + 1, ende1 - 1
call doubleUpdateStochastic(ilut, csf_i, iOrb, excitInfo, weights, negSwitches, &
posSwitches, t, branch_pgen)
! check validity
check_abort_excit(branch_pgen, t)
end do
! then update weights and and to lowering semi-stop
weights = weights%ptr
call calcLoweringSemiStopStochastic(ilut, csf_i, excitInfo, weights, negSwitches, &
posSwitches, t, branch_pgen)
! check validity
check_abort_excit(branch_pgen, t)
do iOrb = ende1 + 1, ende2 - 1
call singleStochasticUpdate(ilut, csf_i, iOrb, excitInfo, weights, posSwitches, &
negSwitches, t, temp_pgen)
branch_pgen = branch_pgen * temp_pgen
! check validity
check_abort_excit(branch_pgen, t)
end do
! and finally to end step
call singleStochasticEnd(csf_i, excitInfo, t)
! if we do RDMs also store the x0 and x1 coupling coeffs
if (tFillingStochRDMOnFly) then
call encode_stochastic_rdm_info(GugaBits, t, rdm_ind= &
contract_2_rdm_ind(i, j, k, l, excit_lvl=2, excit_typ=typ), &
x0=extract_matrix_element(t, 1), &
x1=extract_matrix_element(t, 2))
end if
! todo: think about the additional integral contributions and the
! relative sign of different order influences...
! and not sure yet if in this case i can use this function generally
! for L -> LL -> LL -> L
! and R -> RL -> RL -> R
! since the integral/order influences are different maybe... todo!
! update: on the matrix elements..
! i have to consider the non-overlap excitation, which can lead to
! the same excitation if there is no change in the stepvector
! in the overlap region
! the problem with the L2R2L and R2L2R funcitons is that the
! generator type changes for the non-overlap excitation so the
! matrix elements have to be changed more than in the R2L and L2R case
switch = findFirstSwitch(ilut, t, start2 + 1, ende1)
if (switch > 0) then
integral = extract_matrix_element(t, 2) * (get_umat_el(start1, ende1, ende2, start2) + &
get_umat_el(ende1, start1, start2, ende2)) / 2.0_dp
if (near_zero(integral)) then
branch_pgen = 0.0_dp
t = 0_n_int
else
call encode_matrix_element(t, 0.0_dp, 2)
call encode_matrix_element(t, integral, 1)
end if
else
integral = (-extract_matrix_element(t, 1) * (get_umat_el(start1, ende1, start2, ende2) + &
get_umat_el(ende1, start1, ende2, start2)) * 2.0_dp + (extract_matrix_element(t, 1) + &
extract_matrix_element(t, 2)) * (get_umat_el(start1, ende1, ende2, start2) + &
get_umat_el(ende1, start1, start2, ende2))) / 2.0_dp
if (near_zero(integral)) then
branch_pgen = 0.0_dp
t = 0_n_int
else
call encode_matrix_element(t, 0.0_dp, 2)
call encode_matrix_element(t, integral, 1)
end if
end if
end associate
end subroutine calcDoubleR2L2R_stochastic